1. Field of the Invention
This invention relates to an indicating instrument assembly of any type and more directly to an assembly structure that decreases the depth required for the instrument assembly.
2. Description of the Related Art
Indicating instruments are used for numerous applications across a variety of industries and within innumerable types of machines, systems, and vehicles. Indicating instruments can, for example, measure the speed of a vehicle, such as an automobile or airplane, or measure the rotational speed of an engine shaft or turbine to indicate a need to switch to an appropriate gear ratio so that the motor is not overworked. Indicating instruments can also be fuel, pressure, and temperature gauges, which are found, for example, on vehicles, heavy equipment, assembly line apparatuses, and other industrial equipment. Complex vehicles and other equipment may have a variety of other special purpose indicating instruments to measure any recordable or gaugable activity or condition. For example, airplanes and submarines may have altitude and depth gauges, respectively.
In many situations it is desirable to construct an indicating instrument as small as possible because of size constraints of the environment in which it is used. For example, in an airplane cockpit a large number of instruments must be placed in an extremely limited area. The size of the indicating instrument is considered not only as a factor of its exposed surface area as viewed by an operator, but also in terms of the amount of space taken, for example, under a mounting surface or behind a panel, by the instrument's functional and mounting components.
In other instances, it is desirable that the exposed portion of the indicating instrument be quite large so that the operator can easily perceive the presentation of the gauged information. In these situations, although it may be desirable to provide a large display for the information, it may be equally desirable that the indicating instrument be otherwise small in size due to similar constraints of space for housing or mounting the underlying functional components. An example of these competing needs may be seen in the dashboard instruments of an automobile such as speedometers and tachometers where the dial size is desired to be large for easy reading, but the mounting and housing space within the dashboard is limited.
Indicating instruments may also be manufactured for sale on the “aftermarket,” wherein additional instruments or devices, which were unavailable as options on the vehicle or other equipment at the time of original purchase, are provided for installation by the operator. In the case of aftermarket indicating instruments such as speedometers or tachometers, these gauges may be provided for mounting on top of the dashboard or at another location in the vehicle for ease of viewing by the operator. For example, many aftermarket tachometers are sold to automobile operators involved in stock car racing. In such racing it is important for the operator to know when to shift, but it is imperative that the operator be able to concentrate on the raceway and the competitor vehicles in order to avoid a collision. Many of these racing operators prefer to mount an aftermarket tachometer on top of the dashboard, or otherwise in the area of the windshield, so they do not have to lower their eyes from the road to read an original equipment tachometer mounted within the dashboard.
Prior art indicating instruments 200, such as those shown in FIGS. 1A, 1B, 2A, and 2B, depict aftermarket tachometers with their own housings for dashboard mounting applications. Because of standard design configurations, these indicating instruments 200 are relatively deep in body thickness from the face of the instrument to the back of the housing. The thickness of these instruments 200 is dictated in large part by the size of the meter movement 210, the rear end of which is generally mounted to a printed circuit board (PCB) 230. The meter movement 210 and PCB 230 assembly is then mounted to and within the housing 240 of the indicating instrument 200, generally by mounting screws 220a and 220b, to provide a firm support for the meter movement 210, PCB 230, and related display components of the indicating instrument.
The indicating instrument of FIG. 2B is configured with dual PCBs 230 and 230′, which further increases the necessary depth of the housing to enclose the additional PCB components. Generally a gap is also needed between the PCB 230′ and the rear of the housing 240 in order to allow room for the circuit components mounted on and extending from the PCB 230′, again deepening the housing. The design of mounting screws 220a and 220b, which extend beyond the housing in FIG. 2B, further increase the overall depth of the indicating instrument.
In aftermarket applications, such significant depth of an indicating instrument can make it difficult to fit and install on the dashboard of a vehicle, especially in the case of a narrow dashboard or a steep windshield slope. In applications where the indicating instrument is integrated into the original design of the vehicle, machine, or other system control, the prior art designs of indicating instruments require relatively deep spaces to house their functional components.